1. Field of the Invention
This invention relates to a device and method for treating tissue at a treatment site within the body of a patient, and more particularly to a device and method for promoting myocardial revascularization in a patient.
2. Background of the Invention
A large variety of medical devices and methods have been utilized for treating cardiovascular disease. Many minimally invasive alternatives to conventional procedures such as open heart surgery or cardiovascular bypass surgery for treating heart disease have been developed. Myocardial revascularization is one such minimally-invasive procedure for treating heart disease that avoids the complications that can arise in conventional approaches requiring median sternotomy.
Myocardial revascularization is indicated when the coronary arteries that deliver the heart""s own blood supply become clogged, thereby causing the muscle wall of the heart to be starved of oxygen. Present techniques for myocardial revascularization involve the removal of tissue from the heart wall in the area starved of oxygen, and creating channels though the endocardium into the myocardium. Such present techniques have been successful in promoting the formation of new blood vessels within the myocardium and thereby improving blood perfusion at or near the treatment site.
It was originally believed that the success of the present myocardial revascularization techniques was attributable to the fact that the channels formed in the heart wall remained open, and thus fed blood directly from the interior of the heart into the channels. It has been determined through several independent studies however, that these channels do not remain open for an extended period of time. Experts now believe that the trauma to the to the heart wall sustained during the creation of the channels is responsible for promoting new blood vessels surrounding the treatment site. These new blood vessels subsequently help to supply oxygenated blood to the otherwise underperfused region.
Methods for creating the channels in the heart wall include the use of laser energy, radiofrequency energy, ultrasonic energy, water jet drilling, and mechanical coring. Laser, radiofrequency, and ultrasonic energy methods have the added benefit of creating a thermal trauma to the heart wall while ablating the tissue of the heart.
A second method for stimulating new blood vessel growth involves injecting DNA or protein-based growth factors into the body. Several methods under investigation include systemic, intracoronary, epicardial, endocardial, and intramyocardial injections. It is believed that the most desirable method for injection is intramyocardial delivery. This method provides for drug delivery directly to the site in the heart where new blood vessel growth is desired while avoiding potentially undesirable effects in other regions of the body.
Several studies also suggest that creating an injury at a treatment site produces an increased propensity for the tissue to accept certain growth factors at the treatment sites. It is thus believed that the combination of forming the channels within the heart wall and subsequently infusing growth factor drugs into the treatment sites has advantages over either of the methods by themselves. The combination of injecting neovascularizing growth factors directly into the injury zone surrounding the treatment site can potentially have the greatest positive outcome over all other methods of myocardial revascularization. Present methods for performing the combined procedure involve removing or ablating tissue from the heart wall via thermal or mechanical means and then injecting growth factors either directly into the channel or adjacent to the channel site.
A problem exists, however, in attempting to combine thermal ablation and infusion procedures. After a channel is created in the heart wall and a growth factor is deposited or injected into the channel, a majority of the growth factor will not remain within the heart wall to perform its intended purpose. Unfortunately, the growth factor is squeezed from the open channel and washed away into the blood stream due to the high contractility of the heart wall during systole.
The advantages and purposes of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. These advantages and purposes will be realized and attained by way of the elements and combinations particularly pointed out in the appended claims.
To attain the advantages and in accordance with the purpose of the invention, as embodied and broadly described herein, the invention is directed to a treatment device for body tissue comprising a proximal end assembly including a controller and energy generator and a distal end assembly connected to the proximal end assembly through a body portion. The distal end assembly including a heating portion located distal of a nonconductive portion, the heating portion being operably connected to the controller and energy generator to receive controlled energy therefrom, and the heating portion and nonconductive portion of the distal end assembly are sized so that the heating portion, when inserted into the myocardium of a human heart, is completely located between the epicardium and endocardium, and the nonconductive portion extends through one of the epicardium and endocardium, such that said energy supplied to the heating portion ablates myocardium tissue to form a cavity therein without ablating the epicardium or endocardium.
In accordance with another aspect, the present invention comprises a treatment device for use with body tissue comprising a proximal end assembly including a controller, energy generator and injection assembly and a distal end assembly connected to the proximal assembly through a body portion. The distal end assembly including a heating portion operably connected to the controller and energy generator to receive controlled energy therefrom, and the injection assembly being fluidly connected to the distal end assembly so as to allow fluid to be injected to and through the distal end assembly.
In accordance with yet another aspect, the present invention comprises a method for treating tissue within a body comprising the steps of inserting a distal end assembly of a tissue treatment device into a tissue wall of the body, and forming a cavity completely within surfaces of said tissue wall by supplying controlled energy to a heating portion of the distal end assembly, the energy supplied being sufficient to ablate tissue between the surfaces without ablating a surface of the tissue wall.
In accordance with another aspect, the present invention comprises a method for treating tissue within a body comprising the steps of inserting a distal end assembly of a tissue treatment device into a tissue wall of the body, supplying controlled energy to a heating portion of the distal end assembly to heat the tissue wall, and injecting a treatment fluid from a proximal end of the tissue treatment device through the distal end assembly and into the tissue wall.